1. Field of the Invention
The present invention is directed to a process for dispersing a polyisocyanate in an aqueous medium using a static mixer and optionally chain extending the dispersed polyisocyanate using a second static mixer.
2. Description of the Prior Art
U.S. Pat. No. 4,904,522 discloses the use of polyisocyanate dispersions as binders for fiberglass. Copending application, U.S. Ser. No. 07/529,056, filed May 25, 1990, is directed to reducing the isocyanate content of aqueous polyisocyanate dispersions by reacting the dispersed polyisocyanates with monoamines containing at least one hydroxyl group in order to improve their effectiveness as binders for fiberglass. U.S. Pat. No. 5,191,012, is directed to increasing the pot life of aqueous polyisocyanate dispersions by reacting the dispersed polyisocyanates with polyamines in order to encapsulate the dispersed polyisocyanates and reduce their reactivity to water. U.S. Pat. No. 5,185,200, is directed to to an improved method for reducing the isocyanate content of aqueous polyisocyanate dispersions by reacting the dispersed polyisocyanates with both monoamines containing at least one hydroxyl group and polyamines. Copending application, Ser. No. 07/676,678, is directed to the use of the previously disclosed aqueous polyisocyanate dispersions and modified aqueous polyisocyanate dispersions as sealants and primers for concrete, particularly green concrete.
Because the aqueous polyisocyanate dispersions are not stable due to the reaction of the isocyanate groups with water, it is not possible for a manufacturer to prepare the aqueous polyisocyanate dispersions and ship to them to a potential customer. They must be prepared shortly before they are used in their intended application. Since many potential customers do not have the necessary equipment, a need exists for portable dispersing equipment in order to prepare the dispersions for experimental demonstrations, etc.
In addition, when the aqueous polyisocyanate dispersions are used in applications such as the priming and/or sealing of concrete, the need also exists for portable dispersing equipment since the concrete manufacturers must be able to prepare the dispersions at all of the different locations where they apply concrete.
Accordingly, it is an object of the present invention to provide a method of preparing aqueous polyisocyanate dispersions using equipment which is uncomplicated in design and capable of being moved from one location to another. It is a further object of the present invention to also provide equipment which is capable of chain extending the dispersed polyisocyanates.
These objects may be achieved in accordance with the present invention by using static mixers for the dispersion step and the optional chain extending step.